A road surface state obtaining device disclosed in Patent Document 1 includes an emitting device and a camera. The emitting device emits laser light in a grid shape to a road surface, and the camera takes an image of the grid pattern to form an image. The road surface state obtaining device determines that the road surface is an ascending road surface in the case where a distance between two parallel horizontal lines in the grid pattern is narrower than that in the case where the road surface is flat or horizontal. On the other hand, the road surface state obtaining device determines that the road surface is a descending road surface in the case where the distance between the two parallel horizontal lines in the grid pattern is wider than that in the case where the road surface is flat. The paragraphs [0040] and [0056] have description that coordinates of each intersection of the grid are determined, and the determined coordinates are compared with coordinates in the case of the flat road to detect a three-dimensional shape of the road which includes the gradient of the road and the presence or absence of obstructions and unevenness of the road. Also, Claims 6 and 7 have description that the pattern is divided into a plurality of portions which are emitted one by one in order. This configuration can easily and accurately detect an intersection in the portion of the pattern.
Patent Document 2 discloses a road surface state obtaining device including a preview sensor configured to obtain unevenness of a portion of a road surface which is located in front of the vehicle. Examples of the preview sensor described in the paragraph [0010] include sensors using a laser, ultrasonic waves, or the like, and a sensor using a camera (for detecting unevenness of the road surface based on an image representative of the image-picked-up road surface. Also, Patent Document 2 discloses a system for controlling a suspension based on the unevenness state of the road surface which is obtained by the road surface state obtaining device. Specifically, a future movement of the vehicle is estimated based on the detected unevenness state of the road surface and a current movement of the vehicle such as over-spring vertical acceleration and an over-spring displacement, and control command values are output to the suspension when or before the vehicle passes through the road surface.
Non-Patent Documents 1, 2 disclose a road surface state obtaining device configured to obtain a state of a portion of a road surface which is located in front of a vehicle. This road surface state obtaining device uses a laser displacement sensor as a preview sensor to obtain a relative displacement between an over-spring member and the road surface. A road surface displacement is estimated based on the relative displacement measured by the preview sensor and a change in height position of the preview sensor (e.g., a height position of the over-spring member). The relative displacement measured by the preview sensor includes a displacement of the height position of the over-spring member. Accordingly, a displacement of an over-spring member is estimated, based on an identity observer, using longitudinal acceleration, lateral acceleration, over-spring vertical acceleration, a suspension stroke, an amount of rotation of a rotary actuator, and so on, and a displacement of the road surface is estimated based on the estimated displacement of the over-spring member and the relative displacement measured by the preview sensor.
Also, Non-Patent Documents 1, 2 have description that a suspension system executes FF skyhook control based on a road input and executes preview control in which control command values for an actuator are output a preview compensation time T, before passage of the vehicle through a portion of the road whose state is obtained by the road surface state obtaining device. This configuration can actuate the suspension in accordance with the passage of the vehicle through the road surface even if a delay in the actuator is large, which can satisfactorily suppress a vibration of the over-spring member, improving ride comfort.